// hashtab.cpp

/**
*    Copyright (C) 2014 MongoDB Inc.
*
*    This program is free software: you can redistribute it and/or  modify
*    it under the terms of the GNU Affero General Public License, version 3,
*    as published by the Free Software Foundation.
*
*    This program is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*    GNU Affero General Public License for more details.
*
*    You should have received a copy of the GNU Affero General Public License
*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*
*    As a special exception, the copyright holders give permission to link the
*    code of portions of this program with the OpenSSL library under certain
*    conditions as described in each individual source file and distribute
*    linked combinations including the program with the OpenSSL library. You
*    must comply with the GNU Affero General Public License in all respects for
*    all of the code used other than as permitted herein. If you modify file(s)
*    with this exception, you may extend this exception to your version of the
*    file(s), but you are not obligated to do so. If you do not wish to do so,
*    delete this exception statement from your version. If you delete this
*    exception statement from all source files in the program, then also delete
*    it in the license file.
*/

#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kIndexing

#include "mongo/platform/basic.h"

#include "mongo/db/storage/mmap_v1/catalog/hashtab.h"

#include "mongo/util/log.h"

namespace mongo {

    int NamespaceHashTable::_find(const Key& k, bool& found) {
        found = false;
        int h = k.hash();
        int i = h % n;
        int start = i;
        int chain = 0;
        int firstNonUsed = -1;
        while ( 1 ) {
            if ( !nodes(i).inUse() ) {
                if ( firstNonUsed < 0 )
                    firstNonUsed = i;
            }

            if ( nodes(i).hash == h && nodes(i).k == k ) {
                if ( chain >= 200 )
                    log() << "warning: hashtable " << name << " long chain " << std::endl;
                found = true;
                return i;
            }
            chain++;
            i = (i+1) % n;
            if ( i == start ) {
                // shouldn't get here / defensive for infinite loops
                log() << "error: hashtable " << name << " is full n:" << n << std::endl;
                return -1;
            }
            if( chain >= maxChain ) {
                if ( firstNonUsed >= 0 )
                    return firstNonUsed;
                log() << "error: hashtable " << name << " max chain reached:" << maxChain << std::endl;
                return -1;
            }
        }
    }

    /* buf must be all zeroes on initialization. */
    NamespaceHashTable::NamespaceHashTable(void* buf, int buflen, const char *_name)
        : name(_name) {
        int m = sizeof(Node);
        // log() << "hashtab init, buflen:" << buflen << " m:" << m << std::endl;
        n = buflen / m;
        if ( (n & 1) == 0 )
            n--;
        maxChain = (int) (n * 0.05);
        _buf = buf;
        //nodes = (Node *) buf;

        if ( sizeof(Node) != 628 ) {
            log() << "HashTable() " << _name << " sizeof(node):" << sizeof(Node) << " n:" << n
                  << " sizeof(Key): " << sizeof(Key) << " sizeof(Type):" << sizeof(Type) << std::endl;
            verify( sizeof(Node) == 628 );
        }

    }
}  // namespace mongo
